I have a 20" Bushmaster Upper with a Sight Base, but have no use for it and would like to remove it. Has anyone done this? is the barrel blued underneath? Does it leave any marks? It looks like all you would have to do is remove the flash hider and the two screws on the sight base and slide it right off. Knowing my luck it isn't that easy. Thanks.

hawcer wrote:You might have to knock it off with a brass or hard rubber mallet. Most I have removed from other AR15 barrels are not finished under the gas block.

If you are not going to use the factory take off...would you part with it? I need one for the upper I'm putting together.

Thanks, but the 20" 450 Bushmaster Upper uses a carbine length gas tube so the gas block is actually back inside the free float tube. The sight base I am speaking of only has one purpose and thats for attaching a sight. Do you still want it?

OK my bad, it is actualy a gas block. It just doesn't serve as the gas block block on this rifle. I removed the skrews and "wacked" it a few times pretty hard with a rubber mallet. Still won't break loose. Anyone have any Ideas? Kroil? Thanks

I'm at work so I forget it the retaining part or the block consists of fingers that the screws tighten around the barrel. If there are fingers, pry them gently apart with something and while they're expanded, try again. If no joy, Do you have a heat gun? Heat it up where it wraps around the barrel, trying to not heat the barrel as much as the block. IE create some heat difference. That should expand it enough to break free. If that doesn't work, then you must assume they put some binding agent between it and the barrel. Apply more heat to it in an attempt to soften whatever binding agent they used and give it a whack with the drift hammer. If that doesn't work, I'd go to the torch for even more heat. Use prudence with the torch. IE no need to get it cherry red.

Hoot

In Theory, there is no difference between theory and practice. In Practice, there is.

rsaun867 wrote:OK my bad, it is actualy a gas block. It just doesn't serve as the gas block block on this rifle. I removed the skrews and "wacked" it a few times pretty hard with a rubber mallet. Still won't break loose. Anyone have any Ideas? Kroil? Thanks

The blocks are fortified with a Loc-Tite material. Bushmaster is the only one to do this and it is a great thing to do, if assuring all the gas goes down the tube is the goal, thus eliminating the block as a possible cause for why the bolt might be short stroking.

All loc-tite breaks down at 400 degrees temp. So, a "Little" heat is necessary, but just a LITTLE and don't use anything more than a propane torch. Keep the torch moving all around the block, all the while tapping on the block, so when it frees-up you can immediately stop the heating process.

The useless gas block, is not so useless if you need more gas or different timing, which will be necessary if you hit the port pressure wall and start short stroking. My recommendations are, to just leave it on, it's not hurting anything and if you get into the high end of experimenting with the powders and performance curves, you'll very soon learn why you may need it..t

rsaun867 - which one are you trying to remove? The one hidden underneath the HG or the one forward of the HG? There is 2 on the 20", one functional under the HG, and a cosmetic one forward of it. BTW the cosmetic one is actually a real low profile GB with no tube attached.

2zero6 wrote:rsaun867 - which one are you trying to remove? The one hidden underneath the HG or the one forward of the HG? There is 2 on the 20", one functional under the HG, and a cosmetic one forward of it. BTW the cosmetic one is actually a real low profile GB with no tube attached.

I am trying to remove the cosmetic one forward of the hardguard. Thats the reason I thought it was not a gas block at all. Now i realize that what i was calling a useless sight base, is an actual gas block. It's just not used to direct gas on this rifle. Sorry for the confusion. It sounds like a lot of work due to the Lock Tite. I will try applying a little heat to see if that helps. It just think it would look better without it there. Thanks Guys, again sorry for the confusion, but this rifle does have two gas blocks, not very common.